<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <script src="jQueryTxt.js"></script>
</head>
<body>
<div>aaa</div>
<div>bbb</div>
<span class="header">1</span>
<span class="footer"></span>
<script>
  window.onload = function(){
    $('div').css('color','#999');
    $('.header').css('height','100px');
    $('.header').css('background','#ccc');
    $('.header').css('display','block');
  }
</script>
</body>
</html>
